In recent years, a countermeasure against global warming has focused on a technique for carbon dioxide capture and storage (CCS). Such a technology includes a carbon dioxide capture system that uses an absorbing liquid to capture carbon dioxide contained in exhaust gas (i.e. combustion exhaust gas or process exhaust gas) generated in a thermal power plant, a steel plant, or an waste incineration facility, for example.
One of such carbon dioxide capture systems known in the art is an apparatus that has an absorber and a stripper. The absorber is configured to cause carbon dioxide to be absorbed in an absorbing liquid and generate a rich liquid, the carbon dioxide being contained in exhaust gas supplied by a blower. The stripper is configured to cause carbon dioxide-containing steam to be released from the rich liquid supplied from the absorber, regenerate the rich liquid, and generate a lean liquid. The lean liquid generated by the stripper is supplied to the absorber before a heat exchanger causes heat transfer between the lean liquid and the rich liquid. Moreover, a reboiler coupled to the stripper heats the rich liquid within the stripper using steam supplied from an external and allows carbon dioxide to be released from the rich liquid. Carbon dioxide-containing steam discharged from the stripper is cooled by a cooler and condensed to form condensed water. The condensed water is then separated from the carbon dioxide by a gas-liquid separator. In this manner, the carbon dioxide capture systems capture carbon dioxide contained in exhaust gas.
During the carbon dioxide capture apparatus being operated, the proportion of water contained in the absorbing liquid can fluctuate. For example, the proportion of water contained in the absorbing liquid can fluctuate due to a variation in the amount or flow rate of water contained in exhaust gas supplied to the absorber or due to a circulation flow rate of the absorbing liquid. Such a fluctuation could change the concentration of the absorbing liquid and deteriorate the performance of absorbing carbon dioxide and the rate of capturing carbon dioxide as well. To suppress the lower rate of capturing carbon dioxide, it is desirable that a variation in the proportion of water contained in the absorbing liquid be quickly restrained.